In their cozily tight-knit circle of married friends, which include the coupled Missy (Kristen Wiig) and Ben (Jon Hamm), along with Leslie (Maya Rudolph) and Alex (Chris O’Dowd), Julie (Jennifer Westfeldt) and Jason (Adam Scott) are the single holdouts, still deeply entrenched in the Manhattan dating game. But when their pals begin popping out babies, thereby spending less time with them, the two decide to jump on the procreative bandwagon. Although always strictly just friends, they plan to have a child together yet continue to lead separate romantic lives, thereby solving the need-to-parent problem as well as avoiding the drearily familiar, often combative routine of marriage they see engulfing everybody else.

Friends with Kids could almost play as a follow-up to the far superior and funnier (if flawed) Bridesmaids, with its evolving plotline of what happens after marriage, not to mention certain crucial, shared cast members. But where Wiig and Annie Mumolo’s Bridemaids script had a breezy, improv-y charm, most of writer-director Westfeldt’s effects feel studied and forced. She can and does come up with funny lines, but there are also an awful lot of unoriginal, would-be side-splitters here to plough through. Many of these wisecracks come from the mouth of Alex and are physically demeaning to women in their emphasis on undesirable vagina size, “big racks” and the like, and one senses Westfeldt straining to be daringly edgy in a “See, girls are funny too!” way to rival any of those nasty-minded comic boys, like the Almighty Apatow himself.

Another big problem is the casting. Although Westfeldt and Scott diligently ply their characters’ familiar tropes, with her endearingly gawky, wrong choice-making and his snarky, weisenheimer, too-picky ways which threaten to keep him a bachelor forever, neither of them possesses the true star quality which could make Julie and Jason really riveting. And both actors are none too believable as perfectly doting parents (after an unfunny, if abbreviated, goofily groping copulation scene). Their hard-won baby seems nothing more than a bland, trendy prop for them, although the infant has one moment to “shine,” in a tiresome, cutesy scene involving explosive diarrhea which makes that abysmally similar moment in Bridesmaids seem crafted by Lubitsch.

For that aforementioned star quality, we look to Wiig and Hamm, who share a divine chemistry and are by far the most interestingly complex couple in the film, although they frustratingly get the least screen time. She drowns her marital sorrows in Pinot Grigio, while he has a querulous resentment towards Julie and Jason’s seemingly blissful arrangement, which Hamm conveys with a boldly striking intensity. Meanwhile, O’Dowd is forced to push his likeably bluff, insensitive “typical guy” shtick, and Rudolph shows nothing new or particularly fresh. Edward Burns shows up as a conceivable dream man for Julie but, with his disconcertingly high voice, he has always somehow struck me as a bit on the plastic side, however many salt-of-the-earth types he’s portrayed, and seems far from an ideal happy ending.

The real cast standout is Megan Fox, who plays Mary Jane, a Broadway chorus girl, and proves that, along with her ridiculously refulgent physical endowments, she can act as well. With her forthright declarations about her love of independence and lack of desire for kids, she often seems the most sensible person in the movie. You don’t really believe she’d ever be with a mouthy little nebbish like Jason, but she makes everything else about Mary Jane bracingly, and quite beautifully, convincing.